Planetary Years. The ancients presumed the planets to have definite periods of rulership, at the end of which changes of constitution or environment might be expected to occur to persons or in the places ruled by them. What they called "the shortest years" can be traced to the orbital motions in most cases; but it is difficult to trace a justification for the other groups. They are:

…Planet…..Short..Mean..Greater..Greatest

…Saturn……30….43.5…..57……465

…Jupiter…..12….45…….79……428

…Mars……..15….40…….66……264

…Sun………19….69……120…..1460

…Venus……..8….45…….82……151

…Mercury…..20….48…….76……450

…Moon……..25….66……108……320

By the use of the short years one deduces that, for example, if Saturn conjoins the Moon at birth, its opposition will occur at 15 years of age; if Jupiter conjoins any planet it will form its sextile in 2 years from birth. In other words, it was a method whereby, without the aid of an ephemeris, to determine when the planets wig form aspects or directions to the radical places of the Sun and Moon, and they to the radical places of the planets - called "periodical directions." It is principally of value in mundane astrology, when considering world-trends over long epochs.